In recent years, a lot of research has been done for a light emitting device which (i) generates fluorescence by irradiating a fluorescent material with excitation light by use of an excitation light source and (ii) emits the fluorescence as illumination light. A semiconductor light emitting element, such as a light emitting diode (LED) or a semiconductor laser (LD: Laser Diode), can be used as the excitation light source.
Examples of such a light emitting device encompass a vehicle headlamp disclosed in Patent Literature 1. According to the vehicle headlamp, a semiconductor light emitting element and a fluorescent material are arranged away from each other. A condenser lens is provided between the semiconductor light emitting element and the fluorescent material so as to converge, on the fluorescent material, light received from the semiconductor light emitting element.
Further, a lamp disclosed in Patent Literature 2 has an arrangement in which (i) a fluorescent material is shielded with a reflection mirror having a light transmission section, and (ii) excitation light is emitted from a semiconductor light emitting element provided outside the reflection mirror so as to be incident on the fluorescent material via the light transmission section. According to the arrangement, a lens for converging the excitation light on the fluorescent material is provided (i) between the semiconductor light emitting element and the fluorescent material and (ii) outside the reflection mirror.
That is, according to either the lamp disclosed in Patent Literature 1 or the lamp disclosed in Patent Literature 2, a lens is used to converge, on a single small fluorescent material, the excitation light generated by one or more excitation light sources.